Internal Dose Estimates from Global Fallout Dose Estimates from Global Fallout . H-1. Radiation Dose to the Population of the Continental United States from the Ingestion of Food Contaminated

Appendix H

Internal Dose Estimates from Global Fallout

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Radiation Dose to the Population of the Continental United States from the Ingestion of Food Contaminated with Radionuclides from High-yield Weapons Tests Conducted by

the U.S., U.K., and U.S.S.R. between 1952 and 1963

Final Report

Lynn R. Anspaugh Lynn R. Anspaugh, Consulting

Salt Lake City, UT

Report to the National Cancer Institute Purchase Order No. 263-MQ-008090

September 30, 2000

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Radiation Dose to the Population of the Continental United

States from the Ingestion of Food Contaminated with Radionuclides from Nuclear Tests at the Nevada Test Site

Part I. Estimates of Dose


Salt Lake City, UT


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TABLE OF CONTENTS

Page H- Part I. Estimates of Dose.............................................................................................................................................. 3 Abstract.................................................................................................................................................................. 5 Preface ................................................................................................................................................................... 6 Inroduction............................................................................................................................................................. 7 Methods ............................................................................................................................................................... 10 Nuclear events of interest ............................................................................................................................. 10 Internal dose from 90Sr and 137Cs.................................................................................................................. 10 Deposition density ................................................................................................................................. 11 Integrated intake .................................................................................................................................... 11 Dose coefficients ................................................................................................................................... 14 Age groups............................................................................................................................................. 15 Dose from 131I ............................................................................................................................................... 15 Dose from 3H and 14C ................................................................................................................................... 16 Collective dose.............................................................................................................................................. 18 Results and Discussion ........................................................................................................................................ 19 Doses for individuals .................................................................................................................................... 20 90Sr and 137Cs ......................................................................................................................................... 20 131I.......................................................................................................................................................... 39 Tritium and 14C...................................................................................................................................... 43 Collective dose.............................................................................................................................................. 44 Comparison of per caput effective doses ...................................................................................................... 45 Uncertainty ................................................................................................................................................... 46 Conclusions.......................................................................................................................................................... 46 References............................................................................................................................................................ 48 Part II. Reference and Subsidiary Information........................................................................................................... 50 Comparison of calculated doses with those derived from measurements in foodstuffs....................................... 51 List of significant references................................................................................................................................ 54 Congressional Hearings ................................................................................................................................ 54 Major sources of information on radioactive contamination ........................................................................ 54 Publications related primarily to dose or data directly relevant to dose calculations.................................... 55 Publications related primarily to the detection or monitoring of fallout materials ....................................... 57 Limitations of present calculations of dose from 131I in global fallout ................................................................ 68

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ABSTRACT

According to a Congressional request to the Department of Health and Human Services, a feasibility study is being conducted to study the health consequences to the American peoples of nuclear weapons tests. This report concerns calculations of the dose from the consumption of food contaminated by radionuclides deposited or distributed with global fallout, which originated from high-yield tests conducted in the Northern Hemisphere by the U.S., the U.K. and the U.S.S.R. Such tests were conducted in 19521958 and 19611962. Results of this part of the feasibility study indicate that such doses can be calculated, as have similar doses from the tests conducted at the Nevada Test Site. The methods of calculation for 90Sr, 131I, and 137Cs are based upon the methods developed and used earlier by the Off-Site Radiation Exposure Review Project; these methods employed seasonally adjusted values of radioecological transfer of radionuclides to humans. For 90Sr and 137Cs, doses were calculated on a yearly basis for 1953 through 1972 for each county in the contiguous U.S. for adults and for persons born on 1 January 1951; doses during the latter years were well beyond the time period of the actual tests, but these long-lived radionuclides were still being deposited from the reservoir in the stratosphere. Doses from 131I were estimated only on a country-average basis, as county-by-county deposition levels were not available; doses from 131I were estimated for the 19531963 years. Doses from 3H and 14C were calculated with the use of specific activity models, and calculations were carried out for the actual doses received in 19522000. Detailed results are provided in a CD that accompanies this report. Summary results in the form of coded maps are provided for 90Sr and 137Cs. The total estimated collective effective dose from the five radionuclides considered is estimated to be 66,000 person Sv; the collective dose to the thyroid is 210,000 person Sv. The estimated per caput effective dose is 400 Sv. These doses are somewhat smaller than the doses previously estimated to have occurred in the contiguous U.S. from the atmospheric tests conducted at the Nevada Test Site. The more important radionuclides in global fallout (on an effective dose basis) were 14C and 137Cs, whereas the dose from the Nevada tests is dominated by 131I. A comparison is made of the doses calculated with the current method with doses that can be derived from measurements of global fallout radionuclides in milk as reported by the U.S. Public Health Services Pasteurized Milk Network for the time period of 19601963 first quarter. The results are in good agreement for 90Sr and 131I; calculated results for 137Cs are higher than those based upon the milk measurements, but this is expected as a substantial fraction of dose from 137Cs arises from the consumption of meat. A list is provided of major references concerning the occurrence of global fallout and calculations of dose from these radionuclides. The presently available calculations of dose from 131I in global fallout are limited and are not available on a county-by-county basis. Recommendations are provided on how to improve this situation by the use of measured values of global fallout in milk, other foods, cattle thyroids, and air.

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PREFACE

Congress has asked the Department of Health and Human Services (HHS) to study the health consequences to the American people of nuclear weapons tests. Within that framework a purchase order has been received to assist in the determination of radiation dose to the American people from large atmospheric nuclear weapons tests conducted by the U.S. and the U.K. in the Pacific and by the former U.S.S.R., primarily near the Arctic Circle. Such doses are commonly referred to as resulting from global fallout. The tasks to be performed under the terms of the purchase order are: 1. The primary work to be performed is to prepare crude estimates of the doses of internal

radiation received by the American people as a result of the aboveground tests carried out at sites outside the continental U.S. including the Marshall Islands, Kazakhstan, and Russia. These estimates would be:

Based on a review of the readily available literature and information found in scientific

journals and published reports; it is not expected that sophisticated computer models should be developed or used for this purpose. For the purposes of this assessment, an electronic database of fallout deposition will be provided by NCI;

Averaged over states or latitudinal bands of the continental U.S., with indications on how the high-risk populations could be identified. However, if feasible, primary calculations should be carried out on a county by county basis, and averaged only for presentation purposes;

Calculated separately for the most important radionuclides produced in nuclear weapons tests. These would include, but would not be limited to H-3, C-14, Sr-90, Cs-137, and I-131. Estimates of dose from Sr-90 and Cs-137 will use the deposition databases provided by NCI while estimates of dose from H-3 and C-14 will use methods published by other investigators and by UNSCEAR in its 1993 report as well as in previous reports. Estimates of dose from I-131 will also use the data provided by NCI, though the dose estimates to be reported will be limited to a nationwide collective dose estimate.

Provided in terms of absorbed doses for some of the most radiosensitive organs and tissues (red bone marrow, gastro-intestinal tract, and thyroid).

Calculated by year of testing in the 1950s and 1960s, and summed over the most significant tests worldwide (other than those tests conducted at the Nevada Test Site), with a comparison to the published UNSCEAR latitudinal averages for all tests.

Calculated for persons born on 1 January 1951 and residing continuously in the counties of birth. This calculation will use age-corrected coefficients.

2. For selected areas of the continental U.S. and for selected years of fallout, compare the internal dose estimates calculated in item 1 for Sr-90, Cs-137, and I-131 with those derived from the measurements of fallout radionuclides in foodstuffs.

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3. Provide a list of the most significant references regarding: (1) the networks of measurements of fallout radionuclides in air and foodstuffs, and (2) the assessment of the doses from internal radiation.

4. The report to be provided shall discuss limitations on presently calculating county-specific dose estimates from global sources of I-131 and shall discuss feasibility for future work and methods that might be implemented in such work.

The funds made available to accomplish this work consisted of $24,900. Thus, it was

necessary to find very efficient means to accomplish this complex task.

INTRODUCTION In previous reports (Anspaugh 2000; Beck 1999) doses were estimated for the 48 contiguous states from fallout derived from the tests of nuclear weapons-related devices at the Nevada Test Site (NTS). Results in Beck (1999) were for external exposure and dose, and results in Anspaugh (2000) were for doses from the ingestion of contaminated foods. The latter report was based upon estimates of deposition density as calculated by Beck (1999) for 19 radionuclides. These radionuclides were selected for analysis on the basis of screening calculations that had been performed previously by Ng et al. (1990) for the Off-Site Radiation Exposure Review Project (ORERP); these screening calculations indicated that 21 radionuclides were estimated to be responsible for about 95% of the total dose from the ingestion pathway for the radionuclides released at the NTS. Doses were not calculated in Anspaugh (2000) for two (135I and 239Np) of the 21 radionuclides, as estimates of deposition density were not available* at the time when the calculations were made. Most of the 19 radionuclides had relatively short half lives, but were more important in a dosimetric sense than the long-lived radionuclides due to the rapid entry of local and regional fallout into food chains. For global fallout the radionuclides of concern are different for several reasons. The first is that global fallout by definition consists of radioactive debris that is globally dispersed due to its injection into the high atmosphere by large explosions. Due to its injection at high altitudes, global fallout typically does not return to earth for one or more years. During this time the short-lived fission products decay to small levels, and, except for unusual occurrences, the short-lived radionuclides of interest for NTS fallout are not of concern. Two radionuclides, 90Sr and 137Cs, have long half lives (about 30 y each) and do not decay appreciably before they return to earth. Historically, these radionuclides have been studied extensively due to their presence in global fallout and due to concern about adverse health effects from the ingestion of these two radionuclides. Another factor of importance is that global fallout originates from high-yield weapons that typically derive much of their yield from fusion reactions. These explosions produce or spill large amounts of 3H, and the intense neutron flux also produces large amounts of 14C through the reaction 14N(n,p)14C. Because 3H and 14C enter their respective hydrogen and carbon cycles and do not deposit in the same manner as do radionuclides associated with particulate matter, the usual methods of calculating deposition and dose are not appropriate; rather the * Estimates of deposition density for 239Np are now available from Beck (personal communication). If more detailed studies are to follow the current feasibility studies, the dose from 239Np should be included.

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specific activity approach has been used (UNSCEAR 1993). In order to calculate the dose from 3H and 14C, it is necessary to derive source terms (the activity created per unit fusion-explosion energy) and to estimate the fusion yields as a function of time. In general there is little movement of radionuclides across the hemispheric boundary, so it is also important to know the fusion yield in the northern hemisphere for this assessment. Most of the fusion yields occurred in the northern hemisphere, but with substantial amounts near the equator. The conservative assumption is made here that the resulting radionuclides remained in the northern hemisphere. The fusion yields estimated to have occurred in the northern hemisphere as a function of time are indicated in Table 1. These values were derived from total yield values reported in UNSCEAR (1993), DOE (1994), and Mikhailov et al. (1996); and with subtraction of the fission yields derived by Beck (2000). Due to widespread concern about global fallout and its effects on man, scientists from many countries have studied fallout beginning in the 1950s. Such concern was a primary reason that led to the formation of the United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR), which has studied global fallout over many years and has issued a number of assessments of dose with primary interest on calculating global averages of dose. In its most recent assessment of global-fallout dose the UNSCEAR (1993) provided the estimates indicated in Table 2 of the doses from the ingestion of food contaminated by global fallout. Table 1. Estimated fusion yields exploded in the northern hemisphere as a function of time. Values are estimated from total yields in UNSCEAR (1993), DOE (1994), and Mikhailov et al. (1996); minus the fission yields estimated by Beck (2000). Explosions close to the equator are conservatively considered to have injected their debris into the northern hemisphere only.

Fusion yield, Year megatons

1952 5.0 1953 0.36 1954 17 1955 0.88 1956 13 1957 3.9 1958 31 1959 0 1960 0 1961 69 1962 99 Total 240

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Table 2. Effective dose commitments estimated by UNSCEAR (1993) for the northern temperate zone (4050 latitude) from radionuclides produced by the testing in the atmosphere of large nuclear weapons. Estimates below are for global fallout and arise primarily from the injection of radionuclides into the upper atmosphere of the northern hemisphere.

Radionuclide Dose commitment, Sv 3H 48 14C 78a

55Fe 14 89Sr 2.3 90Sr 170 131I 79

137Cs 280 140Ba 0.42 238Pu 0.0009

239+240Pu 0.50 241Pu 0.004

241Am 1.5 Sum 670

a The UNSCEAR (1993) value of 2600 Sv over all time was multiplied by a factor of 0.03, the portion estimated to be delivered in 5070 y.

On the basis of the data in Table 2, and in accordance with the requirements for the purchase order, the radionuclides selected for examination during this feasibility study include 3H, 14C, 90Sr, 131I, and 137Cs. These radionuclides account for all but a small fraction of the estimated dose to man from global fallout. The prominence of 131I on the list may be surprising, as its half life is only eight days. The appearance of 131I in global fallout has tended to be sporadic, but contaminated milk in the U.S. had been observed on a number of occasions (e.g., Dahl et al. 1963; Terrill et al. 1963). Possible mechanisms for these sporadic occurrences have been suggested by Machta (1963) and include

The subsidence of large air masses contaminated with debris from U.S.S.R. tests at its Novaya Zemlya site near the Arctic Circle, and

The penetration of large thunder storms into the upper troposphere and stratosphere that resulted in the scavenging of fresh debris from the U.S. tests in the Pacific.

The assessment of dose from 14C is particularly difficult, due to its long half life of

5730 y. The UNSCEAR (1993) has assessed the intergenerational dose due to this radionuclide, and under such considerations it is the most significant radionuclide in global fallout. The relative importance of 14C is much less, if the dose during the first 5070 y is considered. Further, the carbon cycle is complex (as evidenced by the current controversy over global warming due to the release of carbon dioxide), and dose assessments must rely on complicated models. Thus, the projections of dose into the future for this radionuclide are only approximate, but estimates of dose through the present time are firmly based upon measurements of 14C in food, water, and humans.

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Estimates of dose from 3H are considered to be more reliable, as this radionuclide has a much shorter half life of 12 y, and the hydrogen cycle is not as complicated as that of carbon. As for 14C, estimates of dose through the present time are firmly based upon measurements of 3H in food, water, and humans. The purpose of this report is to fulfill the requirements of the purchase order referenced in the Preface. The estimates of dose (Task 1) from global fallout for the radionuclides indicated above are summarized in Part I of this report, as are the methods used to perform the calculations. An accompanying CD-ROM contains the detailed results of the calculations on a county-by-county basis for 90Sr and 137Cs; more details of the results for 3H, 14C, and 131I are also provided on the CD, but results for these radionuclides are available only as averages over the continental U.S. Part II of this report contains all other information requested (Tasks 2, 3, and 4).

METHODS

The methods of dose calculation used in this report for 90Sr, 131I, and 137Cs are similar to those used previously for the calculations of dose from tests at the NTS (Anspaugh 2000). The specific activity approach is used to calculate doses from 3H and 14C; the methods used for 3H and 14C are similar to those used by the UNSCEAR (1993). Nuclear events of interest This report includes doses from all high-yield nuclear events that took place within the northern hemisphere during the years from 1952 through 1963; such tests were stopped in 1963 by the U.S., the U.K., and the U.S.S.R. Tests at the NTS are not included in this report, as such tests were not high-yield, and doses from the ingestion of contaminated foods from NTS tests have been included in a previous assessment (Anspaugh 2000). Because tests of high-yield weapons inject much of their debris into the stratosphere from which it devolves slowly over time, it is not generally possible to identify global fallout with a particular test. Rather, doses have been calculated on a monthly basis for 90Sr, 131I, and 137Cs and on a yearly basis for 3H and 14C. Internal dose from 90Sr and 137Cs Doses from 90Sr and 137Cs were estimated by a process similar to that used for radionuclides from NTS fallout (Anspaugh 2000). The basic calculation is shown in equation (1):

gFIPD = , (1) where D = Absorbed dose, Gy, or equivalent/effective dose, Sv; P = Deposition density of the radionuclide of interest at time of fallout arrival, Bq m-2;

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I = Integrated intake by ingestion of the radionuclide per unit deposition, Bq per Bq m-2; and

Fg = Ingestion-dose coefficient for the radionuclide, Gy Bq-1 or Sv Bq-1. Deposition density. Values of deposition density, P, for 90Sr were furnished by Beck (2000) on behalf of the National Cancer Institute (NCI) on a county-by-county basis averaged over each month for the years of 1953 through 1972. Values for the deposition density for 137Cs were derived from those of 90Sr by multiplying the 90Sr results by a factor of 1.5, as recommended by Beck (2000) [a similar relationship has been used by UNSCEAR (1993)]. Integrated intake. Monthly average values of integrated intake, I, were derived from Whicker and Kirchner (1987) by interpolation of the date-specific values in that publication. The age-related values used in this study are shown in Figs. 1 and 2 for 90Sr and 137Cs, respectively. Values of integrated intake are complex functions of age- and season-dependent intake rates of different foods and the season-dependent radioecological movement of radionuclides through food chains. Whicker and Kirchner (1987) developed the PATHWAY model to estimate integrated intake for the ORERP studies. The food-consumption rates used in the

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Dilution of radionuclide concentration in fresh vegetation by plant growth;

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Movement of radionuclides through several soil compartments;

Uptake of a radionuclide through the soil-root system; and

Recontamination of plant surfaces by resuspension and redeposition and by rain splash.

One of the critical factors that is known to vary substantially is the initial retention of fallout by fresh vegetation, particularly when deposition occurs with precipitation (Anspaugh 1987; NCI 1997). The value used for this parameter in PATHWAY is 0.39 m2 kg-1. Its value is known to vary with particle size (and distance from the site of detonation) for dry deposition and with rainfall rate for wet deposition. In addition, values vary substantially for reasons that are not yet explicable. Thus, uncertainty in this parameter contributes substantially to the uncertainty in the estimates of internal dose.

Although the values of integrated intake were originally derived for dry deposition in the semi-arid western areas of the U.S. nearby the NTS, this same value has been used for the entire study performed here. Based upon the experimental data reported by Hoffman et al. (1989), the value of 0.39 m2 kg-1 is actually a reasonable value for retention of radionuclides in rainfall, except during conditions of very light rain when higher values have been observed.

Dose coefficients. The ICRP (1989, 1993, 1995, 1996) has provided compilations of dose coefficients, Fg, for ingestion of radionuclides by members of the general public. These published values, however, are incomplete in the sense that dose coefficients are not listed for all organs for all age groups. Recently, the ICRP (1998) has made available a CD-ROM system that allows the calculation of equivalent and effective doses for all organs for the six age groups considered by the ICRP. The dose-coefficient values provided by the ICRP represent the dose from a given intake that will occur over the next 50 years for adults or until age 70 y for the younger age groups; such values are commonly referred to as coefficients of committed dose.

ICRP (1998) is the source of dose coefficients used for this dose assessment. As for previously performed assessments (Ng et al. 1990), the ICRP dose coefficients have been considered to be average values (or arithmetic means). For the assessment for doses from tests at the NTS (Anspaugh 2000), the ICRP coefficients were converted to geometric means, so that uncertainties could be propagated in a consistent manner. As the deposition-density values provided by Beck (2000) for global fallout do not have attached uncertainty values, the dose coefficients used for this assessment have been used directly from ICRP (1998). The dose coefficients used in this study are indicated in Table 4.

For 90Sr, dose coefficients for the unlisted organs are essentially the same as the dose

coefficient for the thyroid; as 90Sr (and its progeny) is a pure beta-emitting radionuclide that localizes in the bone, the higher doses are to the bone marrow and to the bone surface. The dose coefficient for 90Sr is also somewhat higher for the colon, due to the transit of the beta emitter. On the other hand, 137Cs is distributed throughout the body and delivers most of its dose from the emission of a gamma ray by its short-lived progeny 137mBa. Thus, while dose coefficients for

The six age groups considered by the ICRP are 1) three months [0 to 12 months], 2) one y [from 1 y to 2 y], 3) five y [>2 y to 7 y], 4) 10 y [>7 y to 12 y], 5) 15 y [>12 y to 17 y], and 6) adult [>17 y].

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137Cs for the colon are nearly twice as high as the effective dose coefficient, the dose coefficients for the unlisted organs are approximately the same as the effective dose coefficient.

Table 4. Age-dependent dose coefficients for members of the public used in this study for 90Sr and 131I. Values are from ICRP (1998)

Dose coefficient for the indicated radionuclide and organ, Sv Bq-190Sr 90Sr 90Sr 90Sr 90Sr 137Cs 137Cs

ICRP age

category Bone Sura Colonb Red marrc Thyroid Effective Colon Effective 3 mo 2.3 10-6 1.2 10-7 1.5 10-6 1.2 10-8 2.3 10-7 3.8 10-8 2.1 10-8

1 y 7.3 10-7 8.9 10-8 4.2 10-7 5.5 10-9 7.3 10-8 2.3 10-8 1.2 10-8

5 y 6.3 10-7 4.5 10-8 2.7 10-7 2.9 10-9 4.7 10-8 1.5 10-8 9.6 10-9

10 y 1.0 10-6 2.6 10-8 3.7 10-7 1.8 10-9 6.0 10-8 1.3 10-8 1.0 10-8

15 y 1.8 10-6 1.5 10-8 4.9 10-7 1.1 10-9 8.0 10-8 1.5 10-8 1.3 10-8

Adult 4.1 10-7 1.3 10-8 1.8 10-7 6.6 10-10 2.8 10-8 1.5 10-8 1.3 10-8a Bone surface b Weighted mass average of dose coefficients for the lower and upper large intestine c Red bone marrow

Age groups. Doses were calculated on a county-by-county basis for adults and for an individual who was born on 1 January 1951. Dose from 131I For 131I calculations were also based on eqn (1). Beck (2000) did not provide county-by-county estimates of deposition density for 131I, as more analysis would be required beyond that possible for this feasibility study. Rather, rough estimates of deposition density were provided on a population-weighted basis for the entire country. As for 90Sr and 137Cs, monthly averages of age-dependent integrated intake values were derived from Whicker and Kirchner (1987). The values used in this study are shown in Fig. 5. Dose coefficients were taken from the ICRP (1998); the values used are listed in Table 5. Calculations were made for adults and for individuals born on 1 January in each of the years from 1951 through 1963. In addition, because the dose from ingestion of 131I varies strongly with age, per caput values of dose were calculating by considering the age distribution of the population in 1960 and by calculating a population-weighted average value of dose. For the latter calculation, age-dependent values of integrated intake and dose coefficients were used.

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simulates the worlds hydrological cycle through the use of seven compartments, which consist of atmospheric water, surface soil water, deep groundwater, surface streams and fresh water lakes, saline lakes and inland seas, ocean surface, and the deep ocean. The use of the hydrological cycle is appropriate, as most of the 3H released is in the form of tritiated water or is soon converted to that form (from HT) in soil. Calculations are then made by considering the specific activity of 3H in the various water compartments and the rate of change among the compartments. Example results from the NCRP (1976) model of the dose over time from the release of 1 PBq of 3H to the northern hemisphere are shown in Fig. 6. The annual dose falls off rapidly with time due to the mixing of the released 3H into the larger compartments. The summary result of the data shown in Fig. 6 is that the release of 1 PBq of 3H to the atmosphere in the northern hemisphere would result in a dose of 0.38 nSv to each person living in the hemisphere. The latter result is consistent with the value computed from eqn (2) of 0.27 nSv with consideration of the substantial uncertainty in both results.

The dose from the release of 14C can be assessed in a rather similar way, although the carbon cycle is much more complicated. From UNSCEAR (1982, 1993) the natural production rate of 14C is roughly 1 PBq y-1, and the resulting equilibrium specific activity produces an annual effective dose of about 12 Sv. A calculation similar to that of eqn (2) could be made, but it would be potentially misleading due to the very long half life of 14C and the very long time (more than one individuals life time) to achieve equilibrium. Thus, in order to calculate doses over the first 50 y from the release of 14C, a compartment model for the global circulation of carbon was used. The model chosen is that of Titley et al. (1995), which is the latest model that has been widely accepted and which builds upon previously accepted models. The Titley et al. model is complicated and contains 23 compartments with separate compartments of two to four layers in each ocean. Carbon is considered to be in the form of CO2, which is the form that enters the food chain. The model takes into account temperature changes, photosynthesis in the surface layers of the oceans, and transfer of carbon down the water column.

Example results of model calculations are shown in Fig. 7, which is a plot showing the annual doses from the release of 1 PBq of 14C to the northern hemisphere. The summary result of the data shown in Fig. 7 is that the release of 1 PBq of 14C to the atmosphere of the northern hemisphere would result in a dose of 0.7 Sv to each person living in the hemisphere over the following 50 y.

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For 131I deposition values were not available on a county-by-county basis, but on a population-weighted basis for the entire country. Collective doses were calculated by using the same procedure as mentioned in a previous section for per caput doses. That is, calculations were made with consideration of the age distribution of the population and appropriate values of age-dependent integrated intake and dose coefficient.

For 3H and 14C rough estimates of individual doses were calculated on a country-average

basis; such values do not have an age dependence. Collective doses were calculated by simply multiplying the individual doses for the country by the country population in 1954.

RESULTS AND DISCUSSION The results of the calculations made for this project are provided on a CD that accompanies this report. Information on the CD is organized as follows:

There is one folder labeled SrCs that contains 21 workbooks; 20 are labeled GB1953 through GB1972 and one is labeled GB53-72, which is a summary of the doses for the 20-y period. Each of the 20 workbooks for individual years contains two spreadsheets; the first is labeled Sheet1 and contains county-by-county data for estimates of

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committed dose from 90Sr and 137Cs. Values are provided both for adults and for a person born on 1 January 1951. For 90Sr estimates are provided for bone surface, colon, red marrow, thyroid, and effective dose; for 137Cs estimates are provided for colon and effective doses. The second spreadsheet is labeled Collective and contains calculated values for collective dose on a county-by-county basis. In addition to data for the parameters indicated above, the sum of collective effective dose from both 90Sr and 137Cs is calculated. The summary workbook GB53-72 contains similar data in two spreadsheets, but summarized over the entire period of the calculation.

There is one spreadsheet labeled GBLI131 that contains all calculations for dose from global fallout due to 131I. Calculations are provided for bone surface, colon, red marrow, thyroid, and effective dose for adults and for persons born on 1 January in the years 1951 through 1963. Collective doses and per caput doses are provided on the same spreadsheet; such calculations were made using the fraction of the population falling into various age groups and appropriate values of age-dependent integrated intake and dose coefficient.

A final spreadsheet is labeled TritCarb and contains estimates of dose for 3H and 14C. Doses are estimated on the basis of the inputs of fission yield from Table 1 and the time dependent annual dose factors from Figs. 6 and 7. Each years input is tracked separately and summed for each individual year. The calculations extend through the year 2000.

The intent of the following material is to summarize the data contained on the CD in the

files mentioned above. Doses for individuals 90Sr and 137Cs. Estimates of committed dose are available on the CD-ROM for each county in the contiguous U.S.; values are provided for adults and for a person born on 1 January 1951. For 90Sr estimates are given for dose to the bone surface, colon, red marrow, and thyroid and for effective dose. For 137Cs estimates are given for dose to the colon and for effective dose. Reasons for the selections of these organs are discussed in the Methods Section. Such large amounts of data are more easily summarized graphically. Figs. 823 provide representative results for three years and the sum of committed doses for the entire 19531972 period. Figs. 811 are results for the 1955 year. Figs. 8 and 9 present doses to the red bone marrow from 90Sr for an adult and for a person born on 1 January 1951. Figs. 10 and 11 present effective doses from 137Cs for an adult and for a person born on 1 January 1951. This pattern is repeated for the years of 1959 and 1963; the doses were the highest for the latter year. Finally, Figs. 2023 present doses for the two age groups to the red bone marrow from 90Sr and effective dose from 137Cs that are summed over the entire period of calculation (19531972). The appearance of the maps in Figs. 823 is influenced by the choice of the dose ranges used for the display. There are five dose ranges used for each map, and these dose ranges were selected in the following way with Figs. 8 and 9 used as illustrations. First, all of the data for the committed dose to the selected organ (or effective dose) for the selected radionuclide for the

The 1955, 1959, and 1963 years that are plotted represent local maxima in dose; the committed dose in 1963 (resulting largely from explosions in 1962) was the highest.

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3071 counties for both the adult and the person born on 1 January 1951 were combined into a single file and sorted. For Figs. 8 and 9 this combined file represented the committed doses to the red bone marrow from 90Sr for the adult and for the person born on 1 January 1951 for all 3071 counties. Then, 10% of the 6142 combined sorted doses were assigned the color blue (lower doses) for each map, 25% green, 30% yellow, 25% orange, and 10% red (higher doses). Examination of Figs 8 and 9 indicates several features.

First, it is clear that the higher committed doses from 90Sr occurred to persons living in the eastern third of the country, although there are also hot spots in the Midwest, and in parts of California, Idaho, Oregon, and Washington. These areas of higher committed dose are related primarily to the amounts of rainfall that occurred in these locations. Second, comparison of the two figures indicates that a person born on 1 January 1951 received higher committed doses than a person who was an adult, although these doses are not greatly different. For Figs. 10 and 11 the same technique was used, except that committed effective doses due to 137Cs are plotted. The same geographical pattern is evident, but in this case the dose to the person born on 1 January 1951 is lower than to the adult. Whether doses are higher or lower for a particular age group depends upon 1) the time of year when the fallout occurred, which in turn affects 2) the relative values of the age-dependent integrated intakes [see Figs. 1 and 2], and 3) the values of the age-dependent dose coefficients [Table 4]. The per caput doses over the entire period of analysis are summarized in Table 6 for adults and for a person born on 1 January 1951. In general, the doses calculated for a person born in 1951 from 90Sr are two-three times higher than for the adult, but the doses from 137Cs are essentially the same for the two age groups. The sum of effective doses from 90Sr and 137Cs is 170 Sv for the adult and 210 Sv for the person born in 1951.

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Dose (mSv)0.0000 to 0.00600.0060 to 0.00960.0096 to 0.01230.0123 to 0.01550.0155 to 0.0250

Fig. 8. Map of the committed dose (mSv) for an adult to the red bone marrow from 90Sr deposited during 1955

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Dose mSv0.0000 to 0.00610.0061 to 0.00960.0096 to 0.01230.0123 to 0.01550.0155 to 0.0300

Fig. 9. Map of the committed dose (mSv) for a person born in 1951 to the red bone marrow from 90Sr deposited during 1955.

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Dose (mSv)0.0000 to 0.00230.0023 to 0.00380.0038 to 0.00530.0053 to 0.00740.0074 to 0.0200Other

Fig. 10. Map of the committed effective dose (mSv) for an adult from 137Cs deposited during 1955.

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Fig. 11. Map of the committed effective dose (mSv) for a person born in 1951 from 137Cs deposited during 1955.

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Fig. 12. Map of the committed dose (mSv) for an adult to the red bone marrow from 90Sr deposited during 1959.

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Dose (mSv)0.0000 to 0.00460.0046 to 0.00810.0081 to 0.01110.0111 to 0.01490.0149 to 0.0268Other


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Fig. 16. Map of the committed dose (mSv) for an adult to the red bone marrow from 90Sr deposited during 1963.

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Fig. 20. Map of the committed dose (mSv) for an adult to the red bone marrow from 90Sr deposited during 1953-1972.

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Fig. 21. Map of the committed dose (mSv) for a person born in 1951 to the red bone marrow from 90Sr deposited during 1953-1972.

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Fig. 22. Map of the committed effective dose (mSv) for an adult from 137Cs deposited during 1953-1972.

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Fig. 23. Map of the committed effective dose (mSv) for a person born in 1951 from 137Cs deposited during 1953-1972.

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Table 6. Total per caput doses calculated for the 19531972 period from the deposition of 90Sr and 137Cs in global fallout. Upper values are for adults; lower values are for a person born on 1 January 1951. Values are averaged over the entire U.S.

Individual organ or effective committed dose, Sv Radionuclide Bone surface Colon Red marrow Thyroid Effective

Adult 90Sr 540 17 240 0.86 37 137Cs 160 130 Person born on 1 January 1951 90Sr 1600 34 530 2.3 87 137Cs 160 120

Another way of examining the committed doses for individuals is to look at the sum of effective doses from 90Sr and 137Cs on a county-by-county basis. Such values can be summed for each county over the entire period of 19531972. When this is done, the resulting highest dose of 380 Sv is found in Alpine County, California, and the lowest dose of 6.8 Sv occurred in Imperial County, California, a range of a factor of nearly 60. It is rather surprising that both the lowest and the highest doses occurred in the same state; however, the two counties differ markedly. Alpine County is in the Sierra Nevada Mountains and experiences a high amount of precipitation. Imperial County borders on Mexico and is shadowed by the mountains east of San Diego. Thus, it receives very little precipitation. A list of the 80 counties with the higher estimates of summed committed effective doses is given in Table 7. One of the interesting features of Table 7 is that there are many counties with essentially the same estimated dosethis is to be expected given that global fallout is rather evenly dispersed and that the amount of annual precipitation is the most important factor in determining the amount of global fallout deposited in any one county. Another interesting feature is that the state with the highest number of counties in Table 7 is Iowa (22) followed by Tennessee (14) and North Carolina (11). Counties with the lower estimates of dose are listed in Table 8. Again, it is noted that there is a large number of counties with essentially equal doses, which are lower than those in Table 7 due primarily to the low amounts of annual precipitation in these counties. The state with the highest number of occurrences in Table 8 is Texas (29) followed by California (12) and Washington (9). Three statesCalifornia, Oregon, and Utahcontain counties that occur on both lists. This is due to the highly diverse climatic conditions found in these three states. Fig. 24 is a plot of the country-average sum of committed effective dose from 90Sr and 137Cs as a function of time for two age cohorts: adults in 1951 and those born on 1 January 1951. The influence of changing intake rates and dose coefficients with age is seen. The relative position of the two curves changes as the person born in 1951 ages and is assigned different intake rates and dose coefficients.

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131I. As mentioned above, it was not possible for Beck (2000) to provide estimates of 131I deposition on a county-by-county basis for this feasibility study. Rather, estimates of deposition through time were provided as country-average values. Because the dose from ingestion of 131I is strongly age dependent, dose estimates were calculated for adults and for persons born on 1 January of each of the years 1951 through 1963. The calculations of dose from 131I were not extended through 1972, as was done for 90Sr and 137Cs; this is because testing ended in 1963, and 131I is too short-lived to contribute to doses in the later years. All doses from the ingestion of 131I were estimated on the basis of age- and season-dependent intake factors and age-dependent dose coefficients. Table 7. Counties with higher estimates of total individual effective dose from 90Sr and 137Cs.

State County Dose, Sv State County Dose, Sv CA Alpine 380 TN Bradley 260 SD Lawrence 350 IA Black Hawk 260 CA Tuolumne 350 IA Linn 250 NC Transylvania 320 SD Custer 250 ID Valley 310 NE McPherson 250 CA Mariposa 310 IA Dallas 250 NC Richmond 290 UT Weber 250 NC Polk 280 NC Yancey 250 ID Adams 280 IA Marshall 250 NC Macon 280 IA Delaware 250 NC Clay 280 IA Lucas 250 SD Pennington 270 IA Story 250 ID Fremont 270 IA Audubon 250 NE Logan 270 IN Montgomery 250 NE Thomas 270 MO Harrison 250 ID Boise 270 IN Fountain 250 TN Sequatchie 270 IN Warren 250 IA Taylor 270 IA Dubuque 250 IA Iowa 270 IA Louisa 250 NC Cherokee 270 IA Tama 250 NC Graham 260 WY Teton 250 TN Marion 260 IA Mahaska 250 TN Grundy 260 TN Hamilton 250 VT Lamoille 260 MO Atchison 250 MO Worth 260 TN Mcminn 250 MO Nodaway 260 MO Gentry 250 NE Hooker 260 NE Pawnee 250 NE Nemaha 260 NC Greene 250 NE Richardson 260 NC Lenoir 250 IA Montgomery 260 IA Franklin 250 UT Salt Lake 260 IA Shelby 250 IA Page 260 MO Holt 250 NC Swain 260 MO Putnam 250 TN Bledsoe 260 IA Benton 250 OR Lincoln 260 TN Scott 250 TN Meigs 260 IA Monroe 250 TN Rhea 260 WY Crook 250 TN Van Buren 260 TN Chester 250 IA Jones 260 TN McNairy 250 IA Adair 260

TN Hardin 240

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Table 8. Counties with lower estimates of total individual effective dose from 90Sr and 137Cs.

State County Dose, Sv State County Dose, Sv CA Imperial 6.8 WA Franklin 52 AZ Yuma 14 TX Hudspeth 52 OR Sherman 31 NM Hidalgo 52 AZ Maricopa 31 WA Adams 52 OR Gilliam 31 TX Hidalgo 52 OR Wasco 33 UT Grand 52 TX Presidio 35 NM San Juan 53 NV Clark 36 TX Culberson 53 WA Yakima 37 NM Sierra 53 TX El Paso 38 TX Zavala 54 OR Jefferson 38 CA Orange 54 OR Deschutes 38 TX Live Oak 54 CA Riverside 40 TX Kleberg 54 NM Dona Ana 40 NV Esmeralda 55 CA Merced 40 WA Island 55 TX Zapata 41 CO Costilla 55 WA Benton 42 CA Santa Barbara 56 NM Valencia 43 TX Brooks 56 WA Grant 44 TX Kenedy 56 NM Luna 44 AZ Graham 56 AZ Pinal 44 WA Douglas 57 CA Lassen 44 TX Val Verde 57 TX Brewster 45 TX Jim Wells 57 TX Jim Hogg 47 TX Cameron 57 OR Crook 47 TX Nueces 57 WA Klickitat 48 CO Rio Grande 57 AZ Pima 48 TX Atascosa 58 CA San Joaquin 48 TX Willacy 58 TX Webb 48 TX Uvalde 59 TX Starr 48 NM Catron 59 TX Duval 49 TX Loving 59 OR Wheeler 50 CA San Diego 60 OR Lake 50 UT Wayne 60 CA San Benito 50 CO Conejos 60 NM Socorro 50 TX Frio 60 CA Stanislaus 50 CA Modoc 61 TX Dimmit 51 UT San Juan 61 WA Chelan 51 CA Inyo 61 TX Mcmullen 51 AZ Santa Cruz 62 TX La Salle 51

TX San Patricio 63

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0

10

20

30

40

50

1950 1955 1960 1965 1970 1975

AdultBorn 1 Jan 1951

Sum

yea

rly

com

mitt

ed e

ffec

tive

dose

, S

v

Year

Fig. 24. Plot of the sum of committed effective doses from 90Sr and 137Cs as a function of time for two cohorts: those who were adults in 1951 and those born on 1 January 1951. Most of the variation in the doses between the two cohorts is due to changes in intake rates and in strontium metabolism as the young person ages. The complete set of calculations of dose from the ingestion of 131I is available on the CD-ROM in the workbook entitled GBLI131. The year-by-year estimates of per caput bone surface, colon, red marrow, thyroid, and effective dose are summarized in Table 9. As expected, due to the accumulation of iodine in the thyroid, the dose to this organ is the highest at 960 Sv and the effective dose is less by a factor of 20. The estimates of yearly per caput thyroid dose, along with thyroid doses to the adult and a person born on 1 January 1951, are plotted in Fig. 25. As the person born on 1 January 1951 ages, s/he was assigned the appropriate age-dependent intakes and dose coefficients with time. As indicated, the dose to the young person is substantially higher than the per caput dose and the dose to the adult is substantially lower than the per caput dose. The combined effects on cumulative dose of birth year and of the amount of fallout experienced during a particular year are illustrated in Fig. 26 for persons born on 1 January in the years 1951 through 1963. The highest dose was received by a person born on 1 January 1956. Such a person would have received a substantial dose at a young age from the relative peak of fallout in 1957 and would have still been young enough to have both a high intake and a high dose coefficient for the highest yearly amount of 131I in fallout in

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1962. The person born on 1 January 1951 received less dose, because by the time of the fallout peak in 1962 s/he was older and would have experienced less intake and had a lower

ose coefficient.

ages, as

liable estimates of deposition on a county-by-county basis are not yet available.

ut org e do

d Table 9. Year-by-year estimates of per caput dose from the ingestion of 131I in fallout fromhigh-yield weapons tests in the atmosphere. The estimates below are country averre

Per cap an or effectiv se, Sv Year Bone surface R w Thyroid Effective Colon ed marro

1953 0.0023 0.0045 0.0019 12 0.621954 0.011 0.020 0.0088 56

6 6 1 6

230 12

00021 0.000035 0.000017 0 051

320 16

24 40 19 59 Sum 0.18 0.34 0.15 960 48

2.8 1955 0.0002 0.0004 0.0002 1.3 0.061956 0.031 0.059 0.025 170 8.2 1957 0.021 0.040 0.017 110 5.61958 0.044 0.083 0.036 1959 0.0 0.1 0.01960 0 0 0 0 0 1961 0.011 0.020 0.0088 58 2.91962 0.062 0.11 0.050 1963 0.000 0.000 0.000 1.2 0.0

0

100

200

300

400

500

600

1952 1954 1956 1958 1960 1962 1964

Born 1951Per caputAdult

Ann

ual t

hyro

id d

ose,

G

y

Year Fig. 25. Annual thyroid dose due to the ingestion of 131I from global fallout as a function of year. Data are for three cohorts: those who were adults (18 y in 1953), the per caput value (population-weighted by age), and those born on 1 January 1951.

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0

500

1000

1500

2000

2500

1952 1954 1956 1958 1960 1962

Cum

ula

tive

thyr

oid

dose

, G

y

B irth year

Fig. 26. Cumulative (1953 through 1963) thyroid dose as a function of birth year. Tritium and 14C. The calculated results for the individual effective doses from 3H (tritium) and 14C are given in Table 10. In contrast to the results for 90Sr and 137Cs the values in Table 10 are doses calculated to be actually received in the indicated year, whereas for 90Sr and 137Cs the computed values are for committed doses. The disparate treatments arise from the markedly different behavior of the two groups of radionuclides. Most of the intake of 90Sr and 137Cs will occur in the same year that the radionuclides are deposited in fallout and/or during the next year. However, 3H and 14C are in vapor or gaseous form and do not deposit with particulate matter. Rather, they take substantial time to be distributed throughout the world and their compartments of distribution are very large. Carbon-14 is also very long lived and will contribute to yearly dose for tens of thousands of years. In that regard it does not make sense within the framework of the present project goals to calculate a dose commitment that would be intergenerational. Therefore, the yearly doses for 3H and 14C have been calculated and summed only through the year 2000. As indicated in Table 10, the calculated sums of effective doses through the year 2000 are 66 Sv for 3H and 120 Sv for 14C. The time dependencies of the doses from 3H and 14C are also plotted in Fig. 27, which is on a semi-logarithmic scale. Here, the effects of global distribution, size of compartments, and exchange rates are clearly evident; 3H also has a much, much shorter half life. It is evident that the yearly dose from 3H tracks more closely the amounts injected into the atmosphere, and the yearly dose from 3H subsequently

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decreases fairly rapidly due to its half life. In contrast, 14C takes a long time to be distributed throughout its compartments, the yearly doses track the injection rates only slowly, and the yearly doses decrease with time much more slowly. Table 10. Dose to an individual in the Northern Hemisphere from the creation or release of 3H and 14C from the testing of large fusion weapons in the atmosphere.

Effective dose, Sv Effective dose, Sv Year 3H 14C

Year 3H 14C

1952 0.95 0.032 1977 0.18 2.6 1953 0.20 0.10 1978 0.16 2.4 1954 3.4 0.24 1979 0.14 2.3 1955 0.69 0.51 1980 0.12 2.1 1956 2.8 0.68 1981 0.11 2.0 1957 1.3 0.95 1982 0.097 2.0 1958 6.3 1.3 1983 0.087 1.9 1959 1.1 1.7 1984 0.078 1.9 1960 0.58 1.9 1985 0.069 1.9 1961 14 2.4 1986 0.061 1.8 1962 21 4.0 1987 0.056 1.8 1963 3.8 5.4 1988 0.051 1.7 1964 2.0 5.6 1989 0.046 1.7 1965 1.4 6.2 1990 0.040 1.7 1966 1.1 6.3 1991 0.036 1.6 1967 0.86 5.8 1992 0.033 1.6 1968 0.71 5.3 1993 0.031 1.5 1969 0.59 4.8 1994 0.028 1.5 1970 0.50 4.4 1995 0.025 1.5 1971 0.43 4.1 1996 0.023 1.4 1972 0.38 3.8 1997 0.021 1.4 1973 0.33 3.5 1998 0.019 1.4 1974 0.28 3.2 1999 0.017 1.4 1975 0.24 3.0 2000 0.015 1.3 1976 0.20 2.8 Sum 66 120

Collective dose The collective doses that can be calculated from the data contained in the CD-ROM accompanying this document are summarized in Table 11. The total collective effective dose is estimated to be 66,000 person Sv, and the total collective thyroid dose is estimated to be 210,000 thyroid Sv. In calculating the sum of the dose to the thyroid, it was assumed that the dose to the thyroid from 3H, 14C, and 137Cs was equal to the effective dose. This is a reasonable assumption, as these three radionuclides are distributed uniformly throughout the body.

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0.01

0.1

1

10

100

1950 1960 1970 1980 1990 2000

TritiumCarbon-14

Yea

rly

effe

ctiv

e do

se,

Sv

Year

Fig. 27. Plot of the yearly doses from 3H and 14C calculated on the basis of specific activity models. Due to its large compartments that exchange carbon slowly and its long half life, the dose from 14C tracks the injections more slowly than does the dose from 3H. Table 11. Total collective doses calculated for the 19531972 period from the deposition of 90Sr, 131I, and 137Cs in global fallout and for the 19522000 period from 3H and 14C distributed throughout the Northern Hemisphere. Values are calculated for the 48 contiguous states in the U.S. The sum collective thyroid dose is estimated by summing the specifically calculated thyroid doses and adding the effective doses for 3H, 14C, and 137Cs.

Collective organ or effective committed dose, person Sv Radionuclide Bone surface Colon Red marrow Thyroid Effective 3H 11,000 14C 20,000 90Sr 87,000 2,800 38,000 140 5,900 131I 30 56 24 160,000 7,800 137Cs 25,000 22,000 Sum 210,000 66,000 Comparison of per caput effective doses In Table 12 the doses calculated in this report are compared to similar estimates of dose from global fallout reported in UNSCEAR (1993) as doses averaged over the north temperate zone (4050) of the globe and to values reported previously in Anspaugh (2000)

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for doses averaged over the contiguous U.S. from atmospheric tests conducted at the Nevada Test Site. Examination of Table 12 indicates that the global fallout doses reported in UNSCEAR (1993) are higher than those reported here for 90Sr, 131I, and 137Cs, whereas the UNSCEAR reported doses are lower for 3H and 14C. There are several primary reasons for this: 1) the models used in this study are somewhat different from those used by the UNSCEAR and 2) the assessment domains are different, as the U.S. covers approximately 3050. In general, the agreement between the two studies is reasonable given the relatively large amount of uncertainty in both studies. The UNSCEAR will report on a revised assessment this year that has been made possible by revised information on fission and fusion yields reported for the large yield tests; the UNSCEAR assessment models have also been revised.

Comparison of the doses reported here for the high-yield tests versus those estimated previously for tests conducted at the NTS indicates that the sums of the per caput doses are roughly similar, although the importance of 131I is much greater for the doses from the NTS tests. Also, other short-lived radionuclides are relatively more important for the NTS tests, notably 89Sr and 140Ba. Uncertainty It was not possible for this feasibility study for Beck (2000) to estimate uncertainty in the amounts of monthly depositions of 90Sr and 137Cs on a county-by-county basis or for the country-average values for the monthly deposition of 131I. Thus, no attempt was made to estimate analytically the uncertainty in the estimates of internal dose reported here. Also, the models used to calculate doses from 3H and 14C do not at present allow for the analytical estimation of uncertainty. Based upon the authors subjective judgment, the uncertainty in doses for any individual county is a factor of three or more. The estimates of country-average per caput dose and the estimates of collective dose are likely uncertain by a factor of two or more. It is believed that a substantial amount of uncertainty is associated with estimating the amount of fallout retained by vegetation.

CONCLUSIONS The results reported here are part of a feasibility study to determine if the external and internal doses from fallout from atmospheric tests conducted at the Nevada Test Site and from high-yield tests conducted at other locations can be estimated. Previously reported studies have determined that the internal dose from 131I (NCI 1997) and other radionuclides (Anspaugh 2000) can be determined for tests at the NTS. Similarly, it has been demonstrated that it is feasible to estimate external doses from the tests at the Nevada Test Site (Beck 1999) and from the high-yield tests (Beck 2000). This report completes the individual components of this feasibility study with the demonstration that internal doses from the high-yield weapons tests can be calculated. Except for the dose from 131I and in very general terms, the dose from global fallout (or the dose from high-yield weapons) is more important than the dose from weapons tests at the Nevada Test Site. Also, the external dose tends to be higher than the dose from the ingestion of food contaminated with radionuclides. However, for 131I and in particular the

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dose to the thyroid, the tests conducted at the Nevada Test Site were more important contributors to dose. In fact, for the Nevada tests, 131I contributed about 90% of the total effective dose. Because the variations in dose on a county-by-county basis are very large for the Nevada tests, however, there can be major local variations in this general conclusion. Table 12. Summary of the estimates reported in this paper for per caput doses resulting from the ingestion of contaminated foods in the 48 contiguous states in the United States from fallout from high-yield tests in the atmosphere (global fallout). The current estimates are compared with those reported in UNSCEAR (1993) and with those previously reported for per caput doses from atmospheric tests in Nevada (Anspaugh 2000). Values in the table do not include external doses, which are reported separately by Beck (1999, 2000).

Per caput effective dose commitment, Sv Radionuclide This project UNSCEAR (1993) Nevada Test Site Global fallouta Global falloutb

3H - 66c 48 14C - 120c 78d

55Fe 14 89Sr 17 2.3 90Sr 3.7 37 170 91Sr 0.0065 97Zr 0.15

99Mo 1.0 103Ru 3.8 106Ru 7.2 105Rh 0.086 132Te 7.8

131I 610e 48 79 133I 1.9

136Cs 3.6 137Cs 10 130 280 140Ba 12 0.42 143Ce 0.40 144Ce 5.3 147Nd 1.1 238Pu 0.0009

239+240Pu 1.2 0.50 241Pu 0.087 0.004

241Am 1.5 Sum 680e 400f 670d

a Averaged over the U.S. b North temperate zone (4050). c To the year 2000. d The UNSCEAR (1993) value of 2600 Sv was multiplied by a factor of 0.03, the portion estimated to be delivered in 50 y. e Age corrected. f Incomplete sum for the radionuclides considered.

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REFERENCES

Anspaugh, L. R. Retention by vegetation of radionuclides deposited in rainfallA literature

summary. Livermore: Lawrence Livermore National Laboratory, Livermore; UCRL-53810; 1987.

Anspaugh, L. R. Radiation dose to the population of the continental United States from the ingestion of food contaminated with radionuclides from nuclear tests at the Nevada Test Site. Salt Lake City: L.R. Anspaugh; Report to the National Cancer Institute; P.O. #263-MQ-912901; 2000.

Beck, H. L. External radiation exposure to the population of the continental U.S. from Nevada weapons tests and estimates of deposition density of radionuclides that could significantly contribute to internal radiation exposure via ingestion. New York: H.L. Beck; Report to the National Cancer Institute, P.O. #263-MQ-909853; 1999.

Beck, H. L. External radiation exposure to the population of the continental U.S. from high-yield weapons tests conducted by the U.S., U.K. and U.S.S.R. between 1952 and 1963. New York: H.L. Beck; Report to the National Cancer Institute, P.O. #263-MQ-003539; 2000.

Dahl, A. H.; Bostrum, R.; Patzer, R. C.; Villforth, J. C. Patterns of I131 levels in pasteurized milk network. Health Phys. 9:11791185; 1963.

Department of Energy. United States nuclear tests. July 1945 through September 1992. Las Vegas: U.S. DOE Nevada Operations Office; Report DOE/NV-209 (Rev. 14); 1994.

Hoffman, F. O.; Frank, M. L.; Blaylock, B. G.; von Bernuth, R. D.; Deming, E. J.; Graham, R. V.; Mohrbacher, D. A.; Water, A. E. Pasture grass interception and retention of 131I, 7Be, and insoluble microspheres deposited in rain. Oak Ridge: Oak Ridge National Laboratory; ORNL-6542; 1989.

International Commission on Radiological Protection. Age-dependent doses to members of the public from intake of radionuclides: Part 1. Annals ICRP 20(2). Oxford: Pergamon Press; Publication 56; 1989.

International Commission on Radiological Protection. Age-dependent doses to members of the public from intake of radionuclides: Part 2: Ingestion dose coefficients. Annals ICRP 23(3/4). Oxford: Pergamon Press; Publication 67; 1993.

International Commission on Radiological Protection. Age-dependent doses to members of the public from intake of radionuclides: Part 3: Ingestion dose coefficients. Annals ICRP 25(1). Oxford: Pergamon Press; Publication 69; 1995.

International Commission on Radiological Protection. Age-dependent doses to members of the public from intake of radionuclides: Part 5: Compilation of ingestion and inhalation dose coefficients. Annals ICRP 26(1). Oxford: Pergamon Press; Publication 72; 1996.

International Commission on Radiological Protection. The ICRP database of dose coefficients: Workers and members of the public. Oxford: Pergamon Press; Version 1.0 on CD-ROM; 1998.

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Machta, L. Meteorological processes in the transport of weapon radioiodine. Health Phys. 9:11231132; 1963.

Mikhailov, V. N.; Andryshin, I. A.; Bogdan, V. V.; Vashchinkin, S. A.; Zelentsov, S. A.; Zolotukhin, G. E.; Karimov, V. M.; Kirichenko, V. V.; Matushchenko, A. M.; Silkin, Yu. S.; Strukov, V. G.; Kharitonov, K. V.; Tcdhernyshev, A. K.; Tsrykov, G. A.; Shumaev, M. P. USSR nuclear weapons tests and peaceful nuclear explosions. 1949 through 1990. Moscow: Ministry of the Russian Federation for Atomic Energy and Ministry of Defense of the Russian Federation; 1996.

National Cancer Institute. Estimated exposures and thyroid doses received by the American people from Iodine-131 in fallout following Nevada atmospheric nuclear bomb tests. Washington: NCI Report; 1997.

National Council on Radiation Protection and Measurements. Tritium in the environment. Bethesda: NCRP; Report No. 62; 1979.

Ng, Y. C.; Anspaugh, L. R.; Cederwall, R. T. ORERP internal dose estimates for individuals. Health Phys. 59:693713; 1990.

Rupp, E. M. Age dependent values of dietary intake for assessing human exposures to environmental pollutants. Health Phys. 39:151163; 1980.

Terrill, J. G., Jr. Review of radionuclides in the food chain. In: Fallout, radiation standards, and countermeasures. Washington: U.S. Government Printing Office; Hearings before the Subcommittee on Research, Development, and Radiation, Joint Committee on Atomic Energy; 88th Congress; 1963; Vol. 1:71201.

Titley, J. G.; Cabianca, T.; Lawson, G.; Mobbs, S. F.; Simmonds, J. Improved global dispersion models for iodine-129 and carbon-14. Luxembourg: Commission of European Communities; Report EUR-15880; 1995.

United Nations Scientific Committee on the Effects of Atomic Radiation. Ionizing radiation: Sources and biological effects. New York: United Nations; Sales No. E.82.IX.8; 1982.

United Nations Scientific Committee on the Effects of Atomic Radiation. Sources and effects of ionizing radiation. New York: United Nations; Sales No. E.94.IX.2; 1993.

Whicker, F. W.; Kirchner, T. B. PATHWAY: A dynamic food-chain model to predict radionuclide ingestion after fallout deposition. Health Phys. 52:717737; 1987.

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Radiation Dose to the Population of the Continental United States from the Ingestion of Food Contaminated with Radionuclides from High-yield Weapons Tests Conducted by

the U.S., U.K., and U.S.S.R. between 1952 and 1963

Part II. Reference and Subsidiary Information


Salt Lake City, UT


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COMPARISON OF CALCULATED DOSES WITH THOSE DERIVED FROM

MEASUREMENTS IN FOODSTUFFS One of the specified tasks was to compare the internal dose estimates calculated for 90Sr, 131I, and 137Cs with those derived from the measurements of fallout radionuclides in foods. Extensive measurements of fallout radionuclides in foods started in 1960 with the establishment of the Pasteurized Milk Network (PMN) of the Public Health Service. Additional data were also taken on a limited and/or sporadic basis by many organizations [see PHS (1960)5 for a summary of early measurement efforts], but many of the more sophisticated measurements were not well organized until after the end of the period of testing of high-yield weapons in the atmosphere. A full-scale comparison of the measurements with the dose estimates provided in Part I of this report would be a major undertaking well beyond the limited funds made available for the present study. One of the key issues, of course, is whether the model used in Part I of this study is a reasonable qualitative and quantitative description of the movement of fallout radionuclides to man. The model used for Part I of this study is the PATHWAY model of Whicker and Kirchner (1987).6 During the development of this model it was extensively tested against several data sets, including the measured amounts of global fallout radionuclides in foodstuffs; in addition other data sets were used such as concentrations measured following tests at the Nevada Test Site and following the reactor accident at Windscale, UK. A major report on this subject was published (Kirchner and Whicker 1984).7 This article gives several graphs of long-term comparisons of 90Sr and 137Cs from global fallout in beef and milk. Many additional data sets are provided. The following is an excerpt from the abstract in Kirchner and Whicker (1984):

The statistical tests used to compare the predictions of PATHWAY to the observations include a correlation analysis, a paired t-test, and a binomial test. We use the correlation coefficient between observations and predictions through time to compare the dynamics of the simulated and real world system. Plots of the residuals from regression are then examined for bias between the predictions and observations. The significance of any trends in the residuals is evaluated using a runs test. The paired t-test and the binomial test are used to evaluate the accuracy of PATHWAYs predictions. The hypothesis for the paired t-test is that the ratio of predictions to observations is 1. The paired t-test can be used to test hypotheses about ratios because the distributions of observations and predictions appear to be lognormal. However, the paired t-test does not consider uncertainty in the predictions of the model. We use a binomial test to compare the observed

5 Public Health Service. Radiological Health Data Vol. 1, No. 1; April 1960. 6 See Part I References for citation. 7 Kirchner, T. B.; Whicker, F. W. Validation of PATHWAY, a simulation model of the transport of radionuclides through agroecosystems. Ecological Modeling 22:2144; 1984.

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data to an interval estimate from PATHWAY. The interval corresponds to a 95% confidence interval on the prediction, and is derived from uncertainty analyses that have been conducted on PATHWAY. PATHWAYs predictions are significantly correlated with observed levels of 137Cs and 90Sr in pasture and alfalfa. PATHWAY also simulates the dynamics of 131I, 140Ba, and 137Cs in milk well, but fails to predict what appears to be a long term accumulation of 90Sr in the agro-ecosystem. PATHWAY predicts the absolute concentrations of 131I in milk quite well, but tends to predict levels of 140Ba, 90Sr, 137Cs in milk that are different from those observed by factors of 2 to 7. PATHWAY predicts levels of 137Cs and 90Sr in pasture and beef within a factor of 2 of those observed.

Thus, while the PATHWAY model has been tested extensively and performs quite well, it is not perfect and has been noted to both underpredict and overpredict real world situations. In order to examine some important data sets that pertain directly to global fallout, the data presented to the U.S. Congress by Terrill (1963)8 are used here. The data pertain to the PMN mentioned above. Although data from 62 different locations are available, it is not easy to associate these milkshed data with counties. In addition deposition values for 131I and dose estimates are not available on a county-by-county basis. Therefore, a comparison has been made only for the population-weighted average dose calculated for the 48 states with network-average concentrations, Cm, measured in milk. The relevant milk data are shown in Table 1. The reported concentrations for 90Sr, 131I, and 137Cs have been used as the starting point to calculate effective doses for adults according to the following equation:

K= gm FTLCE where E = Effective dose, Sv; L = Consumption rate of milk, L day-1; T = Number of days in time period, days period-1; Fg = Ingestion-dose coefficient for the radionuclide, Sv Bq-1; and K = Units conversion constant, 0.037 Bq pCi-1. Values of Fg are the same as those used in Part I of this report. A value for L was taken to be 0.42 L day-1, which is consistent with the PATHWAY model values (Whicker and Kirchner 1987). T is either 365 days per year or one fourth of that per quarter. The results of these calculations and the comparisons to the values estimated and reported in Part I of this report are shown in Table 2. A comparison of the values indicates that the dose values for 90Sr and 131I agree quite well, certainly within the expected uncertainties of the values. Dose values for 137Cs do not agree as well, with the model results from Part I being substantially higher. However, a significant amount of the calculated dose from 137Cs would be expected to have occurred from the consumption of contaminated meat; thus, the difference is reasonable. 8 See following list of documents for citation.

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Table 1. Daily average concentration of radionuclides in milk from the 62 stations in the U.S. Public Health Services Pasteurized Milk Network, 1960 through the first quarter of 1963. From Terrill (1963).

Concentration in milk, pCi L-1Time period or parameter 89Sr 90Sr 131I 137Cs 140Ba

1960 12-month average level

LIST OF SIGNIFICANT REFERENCES

Congressional Hearings Over the years Congress has held several hearings on fallout, and the records of the major hearings listed below are major sources of information on fallout. Most of the material is concerned with global fallout, but significant amounts of information pertaining to the Nevada Test Site are also included, particularly in the 1957, 1959, and 1963 hearings. U.S. Congress. The nature of radioactive fallout and its effects on man. Washington: U.S.

Government Printing Office; Hearings before the Special Subcommittee on Radiation, Joint Committee on Atomic Energy; 85th Congress; 1957.

U.S. Congress. Fallout from nuclear weapons tests. Washington: U.S. Government Printing Office; Hearings before the Special Subcommittee on Radiation, Joint Committee on Atomic Energy; 86th Congress; 1959.

U.S. Congress. Radiation standards, including fallout. Washington: U.S. Government Printing Office; Hearings before the Subcommittee on Research, Development, and Radiation, Joint Committee on Atomic Energy; 87th Congress; 1962.

U.S. Congress. Fallout, radiation standards, and countermeasures. Washington: U.S. Government Printing Office; Hearings before the Subcommittee on Research, Development, and Radiation, Joint Committee on Atomic Energy; 88th Congress; 1963.

U.S. Congress. Low-level radiation effects on health. Washington: U.S. Government Printing Office; Hearings before the Subcommittee on Oversight and Investigations, Committee on Interstate and Foreign Commerce, House of Representatives; 96th Congress; 1979.

Major sources of information on radioactive contamination

Health and Safety Laboratory. Fallout quarterly reports. New York: U.S. Department of Energy; 1958+.

Mikhailov, V. N.; Andryshin, I. A.; Bogdan, V. V.; Vashchinkin, S. A.; Zelentsov, S. A.; Zolotukhin, G. E.; Karimov, V. M.; Kirichenko, V. V.; Matushchenko, A. M.; Silkin, Yu. S.; Strukov, V. G.; Kharitonov, K. V.; Tcdhernyshev, A. K.; Tsrykov, G. A.; Shumaev, M. P. USSR nuclear weapons tests and peaceful nuclear explosions. 1949 through 1990. Moscow: Ministry of the Russian Federation for Atomic Energy and Ministry of Defense of the Russian Federation; 1996.

Terrill, J. G., Jr. Review of radionuclides in the food chain. In: U.S. Congress (1963), Vol. 1:71201.

U.S. Department of Energy. United States nuclear tests. Las Vegas: Nevada Operations Office; DOE/NV-209, Rev. 14; 1994.

U.S. Public Health Service. Radiological health data. A series of monthly reports published from April 1960 through December 1974. Washington: U.S. Government Printing

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Office. (Later names of this journal were Radiological Health Data and Reports and Radiation Data and Reports.)

Publications related primarily to dose or data directly relevant to dose reconstruction

berg, B.; Hungate, F. P. Radioecological concentration processes. Proceedings of an international symposium held in Stockholm 2529 April 1966. New York: Pergamon Press; 1967.

Anspaugh, L. R. Retention by vegetation of radionuclides deposited in rainfall: A literature summary. Livermore: Lawrence Livermore National Laboratory; UCRL-53810; 1972.

Barry, P. J.; Chamberlain, A. C. Deposition of iodine onto plant leaves from air. Health Phys. 9:11491157; 1963.

Beierwaltes, W. H.; Crane, H. R.; Wegst, A.; Spafford, N. R.; Carr, E. A., Jr. Radioactive iodine concentration in the fetal human thyroid gland from fall-out. J. Am. Med. Assoc. 173:18951902; 1960.

Beierwaltes, W. H.; Hilger, M. T. J.; Wegst, A. Radioiodine concentration in fetal human thyroid from fallout. Health Phys. 9:12631266; 1963.

Cohn, S. H.; Gusmano, E. A. Uptake and transfer of fallout I131 in pregnant women. Heath Phys. 9:12671269; 1963.

Dunning, G. M. Two ways to estimate thyroid dose from radioiodine in fallout. Nucleonics 14(2):3844; 1956.

Dunning, G. M. Criteria for evaluating gamma radiation exposures from fallout following nuclear detonations. Radiology 66:585594; 1956.

Dunning, G. M. Criteria for establishing short term permissible ingestion of fallout material. Am. Ind. Hyg. Assoc. J. 19:111120; 1958.

Eisenbud, M.; Mochizuki, Y.; Goldin, A. S.; Laurer, G. R. Iodine-131 dose from Soviet nuclear tests. Science 136:370374; 1962.

Eisenbud, M.; Pasternack, B.; Laurer, G.; Block, L. Variability of the I131 concentrations in the milk distribution system of large city. Health Phys. 9:13031305; 1963.

Eisenbud, M.; Pasternack, B.; Laurer, G.; Mochizuki, Y.; Wrenn, M. E.; Block, L.; Mowafy, R. Estimation of the distribution of thyroid doses in a population exposed to I131 from weapons tests. Health Phys. 9:12811289; 1963.

Eisenbud, M.; Mochizuki, Y.; Laurer, G. I131 dose to human thyroids in New York City from nuclear tests in 1962. Health Phys. 9:12911298; 1963.

Garner, R. J. A mathematical analysis of the transfer of fission products to cows milk. Health Phys. 13:205212; 1967.

Koranda, J. J. Agricultural factors affecting the daily intake of fresh fallout by dairy cows. Livermore: Lawrence Livermore National Laboratory; UCRL-12479; 1965.

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Lewis, E. B. Leukemia and ionizing radiation. Science 125:965972; 1957.

Lewis, E. B. Thyroid radiation dose from fallout. Proc. Natl. Acad. Sci. 45:894897; 1959.

Libby, W. F. Dosages from natural radiation and cosmic rays. Science 122:5758; 1955.

Pauling, L. Genetic and somatic effects of carbon-14. Science 128:11831186; 1958.

Rupp, E. M. Age dependent values of dietary intake for assessing human exposure to environmental pollutants. Health Phys. 39:151163;1980.

Stannard, J. N. Radioactivity and health. A history. Springfield, VA: National Technical Information Service; 1988.

Totter, J. R.; Zelle, M. R.; Hollister, H. Hazard to man of carbon-14. Science 128:14901495; 1958.

UNSCEAR. Report of the United Nations Scientific Committee on the Effects of Atomic Radiation. New York: United Nations General Assembly; Official Records: Thirteenth Session, Supplement No. 17 (A/3838); 1958.

UNSCEAR. Report of the United Nations Scientific Committee on the Effects of Atomic Radiation. New York: United Nations General Assembly; Official Records: Seventeenth Session, Supplement No. 16 (A/5216); 1962.

UNSCEAR. Report of the United Nations Scientific Committee on the Effects of Atomic Radiation. New York: United Nations General Assembly; Official Records: Nineteenth Session, Supplement No. 14 (A/5814); 1964.

UNSCEAR. Report of the United Nations Scientific Committee on the Effects of Atomic Radiation. New York: United Nations General Assembly; Official Records: Twenty-First Session, Supplement No. 14 (A/6314); 1966.

UNSCEAR. Report of the United Nations Scientific Committee on the Effects of Atomic Radiation. New York: United Nations General Assembly; Official Records: Twenty-Fourth Session, Supplement No. 13 (A/7613); 1969.

UNSCEAR. Ionizing radiation: Levels and effects. A report of the United Nations Scientific Committee on the Effects of Atomic Radiation to the General Assembly, with annexes. New York: United Nations; Sales No. E.72.IX.17; 1972.

UNSCEAR. Sources and effects of ionizing radiation. United Nations Scientific Committee on the Effects of Atomic Radiation 1977 report to the General Assembly, with annexes. New York: United Nations; Sales No. E.77.IX.1; 1977.

UNSCEAR. Ionizing radiation: Sources and biological effects. United Nations Scientific Committee on the Effects of Atomic Radiation 1982 report to the General Assembly, with annexes. New York: United Nations; Sales No. E.82.IX.8; 1982.

UNSCEAR. Sources, effects and risks of ionizing radiation. United Nations Scientific Committee on the Effects of Atomic Radiation 1988 report to the General Assembly, with annexes. New York: United Nations; Sales No. E.88.IX.7; 1988.

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UNSCEAR. Sources and effects of ionizing radiation. United Nations Scientific Committee on the Effects of Atomic Radiation 1993 report to the General Assembly, with annexes. New York: United Nations; Sales No. E.94.IX.2; 1993.

Visalli, F. I.; Goldin, A. S. Fallout I131 in childrenin vivo measurements. Health Phys. 9:12711277; 1963.

Publications related primarily to the detection or monitoring of fallout materials

Anderson, E. C. Part II. Scintillation counters. The Los Alamos human counter. Brit. J. Radiol. Suppl. 7:2732; 1957.

Anderson, E. C. Radioactivity of people and milk: 1957. Science 128:882886; 1958.

Anderson, E. C.; Schuch, R. L.; Fisher, W. R.; Langham, W. Radioactivity of people and foods. Science 125:12731278; 1957.

Anderson, E. C.; Schuch, R. L.; Fisher, W. R.; Van Dilla, M. A. Barium-140 radioactivity in foods. Science 127:283284; 1958.

Arnalds, O.; Cutshall, N. H.; Nielsen, G. A. Cesium-137 in Montana soils. Health Phys. 57:955958; 1989.

Begemann, F.; Libby, W. F. Continental water balance, ground water inventory and storage times, surface ocean mixing rates and worldwide water circulation patterns from cosmic-ray and bomb tritium. Geochim. Cosmochim. Acta 12:277296; 1957.

Black, S. C.; Potter, G. D. Historical perspectives on selected health and safety aspects of nuclear weapons testing. Health Phys. 51:1733; 1986.

Blincoe, C.; Bohman, V. R.; Fountain, E. L. Iodine-131 in bovine thyroid glands from 1957 through 1961. J. Agr. Food Ch

Documents

Internal Dose Estimates from Global Fallout Dose Estimates from Global Fallout . H-1. Radiation Dose to the Population of the Continental United States from the Ingestion of Food Contaminated